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HOME > Outlooks > Special Outlooks Products > Palmer Drought > Outlook Explanation
 

THE PROBABILITIES ARE OBTAINED BY RUNNING THE CURRENT PALMER DROUGHT DATA FOR EACH CLIMATE DIVISION 4 MONTHS AHEAD USING THE WEATHER SCENARIOS (TEMPERATURE AND PRECIPITATION) OF ALL THE PAST YEARS SINCE AND INCLUDING 1931. THE PROBABILITY IN PERCENT FOR A GIVEN CATEGORY IS THE NUMBER OF TIMES THE PROJECTED PDI FELL IN A GIVEN DROUGHT CATEGORY DIVIDED BY THE NUMBER OF YEARS SINCE 1931 TIMES 100. THE PDI VALUES FOR THE 7 CATEGORIES ARE:

EXTREME OR SEVERE DROUGHT LESS THAN OR EQUAL -3.0
MODERATE DROUGHT GREATER THAN -3.0 AND LESS THAN OR EQUAL -2.0
MILD DROUGHT GREATER THAN -2.0 AND LESS THAN OR EQUAL -1.0
NEAR NORMAL OR INCIPIENT GREATER THAN -1.0 AND LESS THAN CONDITIONS +1.0
MOIST SPELL GREATER THAN OR EQUAL +1.0 AND LESS THAN +2.0
UNUSUAL MOIST SPELL GREATER THAN OR EQUAL +2.0 AND LESS THAN +3.0
VERY OR EXTREME MOIST GREATER THAN OR EQUAL +3.0 SPELL

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Page last modified: September 21, 2005
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